Injectable self-healing hydrogels are being widely used in drug delivery, tissue engineering, and other fields. Because of their excellent biocompatibility and biodegradability, polypeptides are an ideal candidate for preparing injectable self-healing hydrogels. In this study, a polypeptide-based hydrogel with dual response to hydrogen peroxide and light was obtained by copolymerizing 4-arm PEG-amine, N-(p-nitrophenoxycarbonyl)-l-methionine, and N-(p-nitrophenoxycarbonyl)-γ-o-nitrobenzyl-l-glutamate. The hydrogel exhibits injectable self-healing behavior due to the hydrophobic interactions among peptide blocks, which also act as the reservoir of hydrophobic drug molecules. In the presence of hydrogen peroxide or under light irradiation, the thioether bond in methionine was oxidized to sulfoxide, whereas the o-nitro benzyl ester bond was broken to form glutamic acid. As a result, the corresponding hydrophobic blocks of polypeptide become hydrophilic, accelerating the release of drug molecules loaded in the polypeptide hydrophobic blocks. Using this technique, the controlled release of hydrophobic drug molecules was achieved. Our efforts could provide a new strategy for the preparation of self-healing hydrogels based on polypeptides with a dual response to hydrogen peroxide and light. In this view, the practical application of polypeptides in drug delivery, tissue engineering, and other fields, could be expanded and advanced.
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